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<div class="titlepage"><div><div><h4 class="title">
<a name="geometry.reference.algorithms.is_empty"></a><a class="link" href="is_empty.html" title="is_empty">is_empty</a>
</h4></div></div></div>
<p>
          <a class="indexterm" name="idm45246437260704"></a>
Checks if a geometry is the empty set.
        </p>
<h6>
<a name="geometry.reference.algorithms.is_empty.h0"></a>
          <span class="phrase"><a name="geometry.reference.algorithms.is_empty.synopsis"></a></span><a class="link" href="is_empty.html#geometry.reference.algorithms.is_empty.synopsis">Synopsis</a>
        </h6>
<p>
</p>
<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Geometry</span><span class="special">&gt;</span>
<span class="keyword">bool</span> <span class="identifier">is_empty</span><span class="special">(</span><span class="identifier">Geometry</span> <span class="keyword">const</span> <span class="special">&amp;</span> <span class="identifier">geometry</span><span class="special">)</span></pre>
<p>
        </p>
<h6>
<a name="geometry.reference.algorithms.is_empty.h1"></a>
          <span class="phrase"><a name="geometry.reference.algorithms.is_empty.parameters"></a></span><a class="link" href="is_empty.html#geometry.reference.algorithms.is_empty.parameters">Parameters</a>
        </h6>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                  <p>
                    Type
                  </p>
                </th>
<th>
                  <p>
                    Concept
                  </p>
                </th>
<th>
                  <p>
                    Name
                  </p>
                </th>
<th>
                  <p>
                    Description
                  </p>
                </th>
</tr></thead>
<tbody><tr>
<td>
                  <p>
                    Geometry const &amp;
                  </p>
                </td>
<td>
                  <p>
                    Any type fulfilling a Geometry Concept
                  </p>
                </td>
<td>
                  <p>
                    geometry
                  </p>
                </td>
<td>
                  <p>
                    A model of the specified concept
                  </p>
                </td>
</tr></tbody>
</table></div>
<h6>
<a name="geometry.reference.algorithms.is_empty.h2"></a>
          <span class="phrase"><a name="geometry.reference.algorithms.is_empty.returns"></a></span><a class="link" href="is_empty.html#geometry.reference.algorithms.is_empty.returns">Returns</a>
        </h6>
<p>
          Returns true if the geometry is the empty set
        </p>
<h6>
<a name="geometry.reference.algorithms.is_empty.h3"></a>
          <span class="phrase"><a name="geometry.reference.algorithms.is_empty.header"></a></span><a class="link" href="is_empty.html#geometry.reference.algorithms.is_empty.header">Header</a>
        </h6>
<p>
          Either
        </p>
<p>
          <code class="computeroutput"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
        </p>
<p>
          Or
        </p>
<p>
          <code class="computeroutput"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">algorithms</span><span class="special">/</span><span class="identifier">is_empty</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
        </p>
<h6>
<a name="geometry.reference.algorithms.is_empty.h4"></a>
          <span class="phrase"><a name="geometry.reference.algorithms.is_empty.conformance"></a></span><a class="link" href="is_empty.html#geometry.reference.algorithms.is_empty.conformance">Conformance</a>
        </h6>
<p>
          The function is_empty implements function IsEmpty from the <a href="http://www.opengeospatial.org/standards/sfa" target="_top">OGC
          Simple Feature Specification</a>.
        </p>
<h6>
<a name="geometry.reference.algorithms.is_empty.h5"></a>
          <span class="phrase"><a name="geometry.reference.algorithms.is_empty.supported_geometries"></a></span><a class="link" href="is_empty.html#geometry.reference.algorithms.is_empty.supported_geometries">Supported
          geometries</a>
        </h6>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                  <p>
                    Geometry
                  </p>
                </th>
<th>
                  <p>
                    Status
                  </p>
                </th>
</tr></thead>
<tbody>
<tr>
<td>
                  <p>
                    Point
                  </p>
                </td>
<td>
                  <p>
                    <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    Segment
                  </p>
                </td>
<td>
                  <p>
                    <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    Box
                  </p>
                </td>
<td>
                  <p>
                    <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    Linestring
                  </p>
                </td>
<td>
                  <p>
                    <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    Ring
                  </p>
                </td>
<td>
                  <p>
                    <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    Polygon
                  </p>
                </td>
<td>
                  <p>
                    <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    MultiPoint
                  </p>
                </td>
<td>
                  <p>
                    <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    MultiLinestring
                  </p>
                </td>
<td>
                  <p>
                    <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    MultiPolygon
                  </p>
                </td>
<td>
                  <p>
                    <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    Variant
                  </p>
                </td>
<td>
                  <p>
                    <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
                  </p>
                </td>
</tr>
</tbody>
</table></div>
<h6>
<a name="geometry.reference.algorithms.is_empty.h6"></a>
          <span class="phrase"><a name="geometry.reference.algorithms.is_empty.complexity"></a></span><a class="link" href="is_empty.html#geometry.reference.algorithms.is_empty.complexity">Complexity</a>
        </h6>
<p>
          Constant-time
        </p>
<h6>
<a name="geometry.reference.algorithms.is_empty.h7"></a>
          <span class="phrase"><a name="geometry.reference.algorithms.is_empty.example"></a></span><a class="link" href="is_empty.html#geometry.reference.algorithms.is_empty.example">Example</a>
        </h6>
<p>
          Check if a geometry is the empty set
        </p>
<p>
</p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span>

<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">geometries</span><span class="special">/</span><span class="identifier">point_xy</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>


<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
<span class="special">{</span>
    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">model</span><span class="special">::</span><span class="identifier">multi_linestring</span>
        <span class="special">&lt;</span>
            <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">model</span><span class="special">::</span><span class="identifier">linestring</span>
                <span class="special">&lt;</span>
                    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">model</span><span class="special">::</span><span class="identifier">d2</span><span class="special">::</span><span class="identifier">point_xy</span><span class="special">&lt;</span><span class="keyword">double</span><span class="special">&gt;</span>
                <span class="special">&gt;</span>
        <span class="special">&gt;</span> <span class="identifier">mls</span><span class="special">;</span>
    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">read_wkt</span><span class="special">(</span><span class="string">"MULTILINESTRING((0 0,0 10,10 0),(1 1,8 1,1 8))"</span><span class="special">,</span> <span class="identifier">mls</span><span class="special">);</span>
    <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"Is empty? "</span> <span class="special">&lt;&lt;</span> <span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">is_empty</span><span class="special">(</span><span class="identifier">mls</span><span class="special">)</span> <span class="special">?</span> <span class="string">"yes"</span> <span class="special">:</span> <span class="string">"no"</span><span class="special">)</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">clear</span><span class="special">(</span><span class="identifier">mls</span><span class="special">);</span>
    <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"Is empty (after clearing)? "</span> <span class="special">&lt;&lt;</span> <span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">is_empty</span><span class="special">(</span><span class="identifier">mls</span><span class="special">)</span> <span class="special">?</span> <span class="string">"yes"</span> <span class="special">:</span> <span class="string">"no"</span><span class="special">)</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
    <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
        </p>
<p>
          Output:
        </p>
<pre class="programlisting">Is empty? no
Is empty (after clearing)? yes
</pre>
<h6>
<a name="geometry.reference.algorithms.is_empty.h8"></a>
          <span class="phrase"><a name="geometry.reference.algorithms.is_empty.see_also"></a></span><a class="link" href="is_empty.html#geometry.reference.algorithms.is_empty.see_also">See
          also</a>
        </h6>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
              <a class="link" href="num_points.html" title="num_points">num_points</a>
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        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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